A critical flaw has been discovered in the PKIX trust components that allows an X509 credential to be trusted in the special case where no trusted names are available for the given entityID. See External References for the complete details.

External References:

http://shibboleth.net/community/advisories/secadv20150225.txt

It was discovered that HttpResource and FileBackedHttpResource implementations in OpenSAML Java and Shibboleth IdP did not enable hostname verification when using TLS connections. Additionaly, OpenSAML Java makes use of Jakarta Commons HttpClient version 3.x, which does not perform verification of the server hostname against the server's X.508 certificate (CVE-2012-5783). This flaw can be exploited by a Man-in-the-middle (MITM) attack, where the attacker can spoof a valid certificate using a specially crafted subject.

Shibboleth OpenSAML library 2.4.x before 2.4.3 and 2.5.x before 2.5.1, and IdP before 2.3.2, allows remote attackers to forge messages and bypass authentication via an "XML Signature wrapping attack."